diff --git a/library/think/Db.php b/library/think/Db.php
index 4331be12..a75764b7 100644
--- a/library/think/Db.php
+++ b/library/think/Db.php
@@ -70,7 +70,7 @@ class Db
             // 解析连接参数 支持数组和字符串
             $options = self::parseConfig($config);
             if (empty($options['type'])) {
-                throw new Exception('db type error');
+                throw new \InvalidArgumentException('db type error');
             }
             $class = (!empty($options['namespace']) ? $options['namespace'] : '\\think\\db\\connector\\') . ucwords($options['type']);
             // 记录初始化信息
diff --git a/library/think/db/connector/Oracle.php b/library/think/db/connector/Oracle.php
index 19954ecc..7e067aea 100644
--- a/library/think/db/connector/Oracle.php
+++ b/library/think/db/connector/Oracle.php
@@ -125,10 +125,10 @@ class Oracle extends Connection
     /**
      * 取得数据库的表信息（暂时实现取得用户表信息）
      * @access   public
+     * @param string $dbName     
      * @return array
-     * @internal param string $dbName
      */
-    public function getTables()
+    public function getTables($dbName = '')
     {
         $pdo    = $this->linkID->query("select table_name from all_tables");
         $result = $pdo->fetchAll(PDO::FETCH_ASSOC);